In automatic flight control systems, it is well known to provide a velocity stabilization mode (velocity hold mode) wherein the automatic flight control system maintains the aircraft's body referenced velocities constant during operation in the velocity hold mode. This is particularly useful in a variety of aircraft operating conditions to reduce the pilot workload, maximize fuel efficiency, maintain aircraft position with respect to a mission flight plan, and for a variety of other purposes.
During operation in a velocity hold mode, there are a number of situations wherein a pilot may desire to yaw or turn the aircraft while maintaining the velocity hold mode. For example, the pilot may wish to yaw the aircraft to perform a sensor sweep, or for weapons firing. However, during operation in an aircraft body referenced velocity hold mode, the aircraft flight path will change in response to a pilot yaw input. This is illustrated in FIG. 1 wherein an aircraft 10 maintains a constant body referenced velocity both before 11 and after 11a a yaw maneuver, and therefore assumes a new flight path after the maneuver. During certain aircraft operations, and particularly during nap of the earth flight operations wherein the aircraft maintains an altitude close to the ground, a change in aircraft flight path in response to a yaw input may be undesirable. This is true when there are obstacles, e.g.,, buildings, trees, mountains etc., on either side of the flight path which the aircraft may encounter on the change in flight path.